On the NGS front - to re-release a game on the xbox360 wouldn't have been too successful, the majority of 360 owners probably had the original xbox too. PS3 owners are more likely to have not owned a Xbox (like me) and thus, never had the chance to play ninja gaiden, so a re-release was a very welcome purchase for myself.
On the rumble front - on any game other than a racing game it just doesn't work for me. In beat-em-ups it can sometimes make me feel slightly sick (i know i'm in the minority on that one), especially in tekken 5 on the PS2.